1. Field of the Invention
The present invention relates to a power supply voltage control circuit, and more particularly, to an over power supply voltage cut-off circuit which is capable of automatically cutting off a power supply voltage supplying path between a power supply voltage and a system by detecting an over power supply voltage, e.g., where the power supply voltage exceeds a predetermined voltage level, to thereby prevent the system from being damaged or impacted.
The present invention further relates to an overvoltage dropping circuit which is capable of dropping an overvoltage to a normal voltage level when the overvoltage occurs, to thereby provide a stable voltage to a load circuit.
2. Discussion of Related Art
Generally, one of the methods used to protect a specific load from an unstable power supply voltage or a momentary overvoltage is to adopt a fuse on a power supply voltage supplying path. FIG. 1A is a circuit diagram where a conventional over power supply voltage cut-off method is embodied. FIG. 1B is a view of a metal fuse for the case where the method shown in FIG. 1A is applied to a semiconductor device.
Referring to FIG. 1A, a fuse F disposed on the power supply voltage supplying path becomes an open circuit when over (e.g., high) current or voltage flows due to an unstable power supply voltage so that the over power supply voltage is not provided to a load 10 connected to an output terminal of the fuse F.
In this method, the metal fuse as shown in FIG. 1B has a reduced metal area Fa which when blown becomes the open circuit portion.
Once, however, the metal fuse formed within the semiconductor circuit has blown, the recovery of the metal fuse is not possible, thereby resulting in the destruction of the semiconductor circuit.
Alternatively, if replaceable and the fuse as shown in FIG. 1A is cut off or blown, it has to be replaced with new one by a user which is inconvenient for the user.